Speedup, cost reduction, noise reduction, and the like are required of the foregoing various motors, in addition to high accuracy in rotation. One of components to determine required performance is a bearing for supporting a spindle of the motor. In recent years, a fluid bearing having superior characteristics in the foregoing required performance is contemplated using, or actually used.
This type of fluid bearing is broadly divided into a dynamic pressure bearing and a so-called cylindrical bearing (a bearing the bearing surface of which is in the shape of a perfect circle). The dynamic pressure bearing is provided with dynamic pressure generation means which makes a lubricating oil in a bearing gap generate dynamic pressure. The cylindrical bearing is not provided with such dynamic pressure generation means.
Taking the case of a fluid bearing device which is installed in the spindle motor of the disk device such as the HDD and the like, for example, the fluid bearing device is provided with a radial bearing portion for supporting an axial member in a non-contact manner rotatably in a radial direction, and a thrust bearing portion for supporting the axial member rotatably in a thrust direction. As the radial bearing portion, a dynamic bearing, which is provided with grooves (dynamic pressure generating grooves) in the inner peripheral surface of a bearing sleeve or in the outer peripheral surface of the axial member to generate dynamic pressure, is used. As the thrust bearing portion, for example, a dynamic bearing, which is provided with dynamic pressure generating grooves in both end faces of a flange part of the axial member, or in surfaces opposed thereto (an end face of a bearing sleeve, an end face of a thrust member fixed on a housing or the like), is used (refer to, for example, Japanese Patent Laid-Open Publication No. 2000-291648). Otherwise, there are cases where a bearing (so-called pivot bearing), which supports one end face of the axial member in a contact manner by a thrust plate, is used as the thrust bearing portion (refer to, for example, Japanese Patent Laid-Open Publication No. 11-191943).
The bearing sleeve is generally fixed in a predetermined position of the inner periphery of the housing. A seal member is disposed on an opening of the housing in most cases, in order to prevent the lubricating oil in an internal space of the housing from leaking to the outside.
The fluid bearing device having a construction described above comprises parts such as a housing, a bearing sleeve, an axial member, a thrust member, and a seal member, and an effort is under way to increase the accuracy of finishing and assembling of each part, for the purpose of ensuring high bearing performance, which is required in accordance with increase in the performance of the information equipment more than ever. Demand for cost reduction on this type of fluid bearing device, on the other hand, has increasingly become stringent in accords with a tendency toward drop in price of the information equipment.
One of important points for reducing cost of this type of fluid bearing device is efficiency in an assembling process. Namely, the housing and the bearing sleeve, the housing and the thrust member, and the housing and the seal member are generally bonded to each other by use of an adhesive in most cases. However, it takes relatively long time from application of the adhesive to solidification thereof, so that bonding is part of the reason of reducing the efficiency in the assembling process. Also, there is concern about the occurrence of outgassing due to the adhesive, as well as the possibility of degradation of adhesion with a lapse of time.